vfs: bury ->get_sb()

This is an ex-parrot.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 4471a41..2e994ef 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -166,13 +166,11 @@
 	void (*kill_sb) (struct super_block *);
 locking rules:
 		may block
-get_sb		yes
 mount		yes
 kill_sb		yes
 
-->get_sb() returns error or 0 with locked superblock attached to the vfsmount
-(exclusive on ->s_umount).
-->mount() returns ERR_PTR or the root dentry.
+->mount() returns ERR_PTR or the root dentry; its superblock should be locked
+on return.
 ->kill_sb() takes a write-locked superblock, does all shutdown work on it,
 unlocks and drops the reference.